Recently, by the improved performance of computers, it became possible to make a plurality of virtual computers (virtual machines, hereinafter referred to as “VMs”) operate in a physical computer. A VM performs various types of processing by starting up an operating system (hereinafter referred to as an “OS”) installed in a virtual storage device (a Virtual Hard Disk Drive, hereinafter referred to as a VHDD).
Furthermore, a technology of creating a snapshot (a child file) for which write can be performed from a parent file in a file system is known (Patent Literature 1). According to this technology, if write occurs in a snapshot, differential data which occurred by write is stored in another storage area than the snapshot, and the storage destination of the differential data is changed to the other storage area. By utilizing the writable snapshot, the commonly utilized OSs, applications, and others can be created from an image referred to as a Golden Image (a parent file which has no parent thereof and is hereinafter also referred to as a GI) into a plurality of VMs.
Furthermore, a technology for being able to uniquely identify a volume in a plurality of storage apparatuses is published (Patent Literature 2). According to this technology, by sharing an identifier for making a volume and a storage apparatus unique among a plurality of storage apparatuses, the operation for a specific volume can be performed among the plurality of storages.